Changes between Version 9 and Version 10 of kernel_syscalls

Timestamp:

Oct 29, 2014, 5:07:08 PM (10 years ago)

Author:

alain

Comment:

--

kernel_syscalls

@@ -1 +1 @@
 = GIET-VM  / Syscall Handler =
 
-The [source:soft/giet_vm/giet_kernel/sys_handler.c sys_handler.c] and [source:soft/giet_vm/giet_kernel/sys_handler.h sys_handler.h] files define the kernel data structure and functions that are used to handle the system calls. They are prefixed by ''_'' to remind that they can only be executed by a processor in kernel mode.
+The [source:soft/giet_vm/giet_kernel/sys_handler.c sys_handler.c] and [source:soft/giet_vm/giet_kernel/sys_handler.h sys_handler.h] files define the kernel data structure and functions that are used to handle the system calls. These functions are prefixed by ''_'' to remind that they can only be executed by a processor in kernel mode.
 
 [[PageOutline]]
@@ -63 +63 @@
 
 
+== __ FBF related syscall handlers__==
+
+There exist two methods to access the ''vci_framebuffer'':
+ * The _sys_fbf_sync_write() and _sys_fbf_sync_read() functions use a memcpy strategy to implement the transfer between a data buffer (user space) and the frame buffer (kernel space). They are blocking until completion of the transfer.
+ * The _sys_fbf_cma_alloc(), _sys_fbf_cma_start(),  _sys_fbf_cma_display(), and _sys_fbf_cma_stop() functions use the ''vci_chbuf_dma'' component to transfer a stream of images from an user space chained buffer (two buffers) to the frame buffer. 
+ 
+ === int '''_sys_fbf_sync_write'''( unsigned int offset,  void* buffer,   unsigned int length ) ===
+This function transfer data from an user buffer to the frame_buffer device using a memcpy. 
+ * '''offset''' : offset (in bytes) in the frame buffer.
+ * '''buffer''' : base address of the memory buffer.
+ * '''length''' : number of bytes to be transfered.
+
+ === int '''_sys_fbf_sync_read'''( unsigned int offset,  void* buffer,   unsigned int length ) ===
+This function transfer data from the frame_buffer device to anuser buffer using a memcpy.
+ * '''offset''' : offset (in bytes) in the frame buffer.
+ * '''buffer''' : base address of the memory buffer.
+ * '''length''' : number of bytes to be transfered.
+
+ === int '''_sys_fbf_cma_alloc'''() ===
+This function allocates a private CMA channel to the calling task, and register the channel index in the task context.
+Return -1 if no CMA channel available.
+ 
+ === int '''_sys_fbf_cma_start'''( void* vbase0,  void* vbase1,  unsigned int length ) ===
+This function initializes the CMA channel to start the transfer of a stream of images from an user chbuf (two buffers) to the frame buffer chbuf (one single buffer). The user buffers must be aligned on a word boundary.
+ * '''vbase0''' : virtual base address of the first user buffer.
+ * '''vbase1''' : virtual base address of the second user buffer.
+ * '''length''' : buffer length (bytes)
+It uses the _fbf_chbuf[] and _fbf_chbuf_paddr[] arrays, that are both indexed by the channel index, and makes the following actions: 
+1. it computes the physical addresses for the two source user buffers, for the destination frame buffer, and initializes the channel descriptor _fbf_chbuf[i].
+2. it computes the physical address for the chbuf descriptor and register it in the _fbf_chbuf_paddr[i]. 
+3. it makes a SYNC request to L2 cache for channel descriptor if the IOB is used, because the channel descriptor is directly accessed in XRAM by the CMA component.
+4. it Starts the CMA hardware channel, that will poll the channel descriptor to fransfer an user buffer to the frame buffer as soon as the source user buffer is marked valid.
+Return 0 in case of success. 
+Return -1 if no CMA channel allocated to the calling task, or if user buffers not aligned on a word boundary.
+
+ === int '''_sys_fbf_cma_display'''( unsigned int index ) ===
+This function is used in conjunction with the _fbf_cma_start() function, and must be called each time a new user buffer is available for display, to set the user buffer status in the chbuf descriptor.
+The '''buffer'''  argument define the user buffer index (0 => buf0 / not 0 => buf1).
+It makes the following actions if the IO Bridge component is used:
+1. it makes an INVAL request for the channel descriptor, before testing the source buffer status, because it is modified in XRAM by the CMA component.
+2. it makes a SYNC request for the source user buffer before activating the CMA  transfer, because the data will be read from XRAM by the CMA component.
+3. it makes a SYNC request for the channel descriptor after modification of the SRC and DST status, because these descriptors will be read from XRAM by the CMA component.
+Return 0 in case of success.
+Return -1 if no CMA channel allocated to the calling task.
+
+ === int '''_sys_fbf_cma_stop'''() ===
+This function  desactivares the CMA channel  allocated to the calling task.
+Return 0 in case of success.
+Return -1 if no CMA channel allocated to the calling task.
+
+
+
+
 == __Miscelaneous syscall handlers__ ==